Dosing and mixing arrangement for use in exhaust aftertreatment

ABSTRACT

A method for causing exhaust gas flow to flow at least 270 degrees in a first direction about a perforated tube using a baffle plate having a main body with a plurality of flow-through openings and a plurality of louvers positioned adjacent to the flow-through openings. The method includes deflecting a first portion of the exhaust gas flow with the main body of the baffle plate. The method also includes allowing a second portion of the exhaust gas flow to flow through the flow-through openings of the baffle plate. The method also deflects the second portion of the exhaust gas flow at a downstream side of the main body with the louvers hereby causing the second portion of the exhaust gas flow to flow in the first direction about the perforated tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/356,541,filed Mar. 18, 2019, now U.S. Pat. No. 10,603,642, which is acontinuation of application Ser. No. 15/650,502, filed Jul. 14, 2017,now U.S. Pat. No. 10,245,564, which is a continuation of applicationSer. No. 14/180,953, filed Feb. 14, 2014, now U.S. Pat. No. 9,707,525,which application claims the benefit of provisional application Ser. No.61/765,371, filed Feb. 15, 2013, which applications are incorporatedherein by reference in their entirety.

BACKGROUND

Vehicles equipped with internal combustion engines (e.g., dieselengines) typically include exhaust systems that have aftertreatmentcomponents such as selective catalytic reduction (SCR) catalyst devices,lean NOx catalyst devices, or lean NOx trap devices to reduce the amountof undesirable gases, such as nitrogen oxides (NOx) in the exhaust. Inorder for these types of aftertreatment devices to work properly, adoser injects reactants, such as urea, ammonia, or hydrocarbons, intothe exhaust gas. As the exhaust gas and reactants flow through theaftertreatment device, the exhaust gas and reactants convert theundesirable gases, such as NOx, into more acceptable gases, such asnitrogen and water. However, the efficiency of the aftertreatment systemdepends upon how evenly the reactants are mixed with the exhaust gases.Therefore, there is a need for a flow device that provides a uniformmixture of exhaust gases and reactants.

SCR exhaust treatment devices focus on the reduction of nitrogen oxides.In SCR systems, a reductant (e.g., aqueous urea solution) is dosed intothe exhaust stream. The reductant reacts with nitrogen oxides whilepassing through an SCR substrate to reduce the nitrogen oxides tonitrogen and water. When aqueous urea is used as a reductant, theaqueous urea is converted to ammonia which in turn reacts with thenitrogen oxides to covert the nitrogen oxides to nitrogen and water.Dosing, mixing and evaporation of aqueous urea solution can bechallenging because the urea and by-products from the reaction of ureato ammonia can form deposits on the surfaces of the aftertreatmentdevices. Such deposits can accumulate over time and partially block orotherwise disturb effective exhaust flow through the aftertreatmentdevice.

SUMMARY

An aspect of the present disclosure relates to a method for dosing andmixing exhaust gas in exhaust aftertreatment. Another aspect of thepresent disclosure relates to a dosing and mixing unit for use inexhaust aftertreatment. More specifically, the present disclosurerelates to a dosing and mixing unit including a baffle plate configuredto direct exhaust gas flow to flow around a perforated mixing tube toeffectively mix and dose exhaust gas within a relatively small area.

An aspect of the disclosure includes a method for causing exhaust gasflow to flow at least 270 degrees in a first direction about aperforated tube using a baffle plate. The baffle plate has a main bodythat defines a plurality of flow-through openings. The baffle plate alsoincludes a plurality of louvers positioned adjacent to the flow-throughopenings. The main body of the baffle plate has an upstream side and adownstream side. The louvers are positioned at the downstream side ofthe main body of the baffle plate. The downstream side of the main bodyof the baffle faces toward the perforated tube. The method includesdeflecting a first portion of the exhaust gas flow with the upstreamside of the main body of the baffle plate thereby causing the firstportion of the exhaust flow to flow around an end of the main body ofthe baffle plate and around the perforated tube in the first direction.The method also includes allowing a second portion of the exhaust gasflow to flow through the flow-through openings of the baffle plate fromthe upstream side of the main body to the downstream side of the mainbody. The method also involves deflecting the second portion of theexhaust gas flow at the downstream side of the main body with thelouvers thereby causing the second portion of the exhaust gas flow toflow in the first direction about the perforated tube.

A variety of additional aspects will be set forth in the descriptionthat follows. These aspects can relate to individual features and tocombinations of features. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restrictive of the broad concepts uponwhich the embodiments disclosed herein are based.

DRAWINGS

FIG. 1 is a perspective view of a dosing and mixing unit having featuresthat are examples of inventive aspects in accordance with the principlesof the present disclosure;

FIG. 2 is a side perspective view of the dosing and mixing unit of FIG.1 with interior components visible;

FIG. 3 is a side view of the dosing and mixing unit of FIG. 2;

FIG. 4 shows exhaust gas flowing through the dosing and mixing unit ofFIG. 3;

FIG. 5 is a top plan view of the exhaust gas flowing through the dosingand mixing unit of FIG. 3;

FIG. 6 is a perspective view of an example baffle curving partiallyaround an example perforated tube suitable for use in the dosing andmixing unit of FIG. 2;

FIG. 7 is a perspective view showing a downstream side of the baffle ofFIG. 6;

FIG. 8 is a side elevational view of the baffle of FIG. 6;

FIG. 9 is a cross-sectional view of the dosing and mixing unit of FIG. 2taken along the 9-9 line of FIG. 3;

FIG. 10 is a side view of the dosing and mixing unit of FIG. 2 with aperforated plate disposed between the inlet and the treatment substrate;

FIG. 11 is a front view of an example perforated suitable for use in thedosing and mixing unit of FIG. 10; and

FIG. 12 shows exhaust gas flowing through the dosing and mixing unit ofFIG. 10.

DETAILED DESCRIPTION

Reference will now be made in detail to the exemplary aspects of thepresent disclosure that are illustrated in the accompanying drawings.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like structure.

FIGS. 1-5 show a dosing and mixing unit 10 in accordance with theprinciples of the present disclosure. The dosing and mixing unit 10includes a housing 12 having a housing body 30, an inlet 18, and anoutlet 20. An exhaust treatment substrate 50, a perforated tube 40, anda baffle 52 are disposed within the housing 12 (FIG. 2). Exhaust gas Gflows from the inlet 18, through the treatment substrate 50, through thebaffle 52, and into the tube 40 (see FIG. 4). The baffle 52 isconfigured to direct the exhaust gas G to flow in a direction d (seeFIG. 3) about the perforated tube 40 to enhance swirling within the tube40. The tube 40 defines the outlet 20 of the unit 10.

As shown in FIG. 3, the housing body 30 defines a central housing axis32 between a first end 34 and a second opposite end 36. A length L ofthe main housing body 30 extends along the central housing axis 32between the first and the second ends 34, 36 of the main housing body 30(FIG. 3). The inlet 18 is adjacent the first end 34 of the main housingbody 30 and the outlet 20 is adjacent the second end 36 of the mainhousing body 30. The exhaust treatment substrate 50 is positioned withinthe main housing body 30 between the inlet 18 and the perforated tube40. The main housing body 30 defines an interior volume V (see FIG. 3)that extends between an exhaust treatment substrate 50 and theperforated tube 40. The interior volume V defines a transversecross-sectional area A that is transverse relative to the centralhousing axis 32 (see FIG. 9).

The perforated tube 40 is disposed towards the second end of the mainhousing body 30. In certain embodiments, the second end 36 of the mainhousing body 30 includes a curved portion 46 that curves partiallyaround the perforated tube 40. As used herein, a “perforated tube” is aconduit having a plurality of side holes. The use of the term“perforated” is not dependent on the method(s) used to make the sideholes (i.e., the holes can be made in any way and need not be formed bya stamping/perforation type process). The perforated tube 40 defines atube axis 42 aligned at an angle θ relative to the central housing axis32 (see FIG. 5).

The baffle plate 52 is positioned within the interior volume V betweenthe perforated tube 40 and the exhaust treatment substrate 50. Incertain embodiments, the baffle plate 52 is separate from and notconnected to the perforated tube 40. As shown in FIGS. 6-8, the baffleplate 52 includes a main plate body 54 having an upstream side 56 thatfaces toward the exhaust treatment substrate 50 and a downstream side 58that faces toward the perforated tube 40 (also see FIG. 3). In certainembodiments, the main body 54 of the baffle plate 52 extends onlypartially around the perforated tube 40. In certain embodiments, themain body 54 of the baffle plate 52 extends along less than fiftypercent of a circumference of the perforated tube 40. In certainembodiments, the main body 54 of the baffle plate 52 extends along lessthan one-third of a circumference of the perforated tube 40. In certainembodiments, the main body 54 of the baffle plate 52 extends along lessthan one-quarter of a circumference of the perforated tube 40.

In certain embodiments, the main body 54 of the baffle plate 52 has acurvature defined by an arc having a radius centered on a centerline ofthe perforated tube 40. In some embodiments, the upstream side 56 of themain body 54 has a convex curvature and the downstream side 58 of themain body 54 has a concave curvature (see FIG. 8). In some of theseembodiments, the convex and concave curvatures curve partially aroundthe perforated tube 40 (see FIG. 3).

The main plate body 54 defines a plurality of flow-through openings 60that extend through the main plate body 54 between the upstream anddownstream sides 56, 58 of the main plate body 54. The openings 60enable treated exhaust gas G to flow through the baffle 52 towards thetube 40 (see FIGS. 4 and 5). In certain embodiments, the perforated tube40 defines circular openings 45 and the baffle plate 52 definesrectangular openings 60. In certain embodiments, the openings 45 of theperforated tube 40 are smaller in area than the openings 60 in thebaffle plate 52.

In accordance with some aspects of the disclosure, the baffle plate 52also includes one or more louvers 62 positioned adjacent to theflow-through openings 60 of the main plate body 54. In someimplementations, the louvers 62 are disposed at the downstream side 58of the plate body 54. In other implementations, one or more louvers 62can be positioned at the upstream side 56 or at both the upstream anddownstream sides 56, 58 of the plate body 54. In certain embodiments,the louvers 62 have base ends 63 that are integral/unitary with the mainbody 54 of the baffle plate 52. Free ends 65 of the louvers 62 extendlaterally away from the main plate body 54. The louvers 62 direct thegas G passing through the openings 60 in a flow direction d (FIG. 3)around the tube 40. The flow direction d generated by the louvers 62encourages the swirling exhaust gas G to remain within the perforatedtube 40 once the exhaust gas G has entered the perforated tube 40.Treated gas G also flows beneath the free edge 66 of the baffle 52towards the curved portion 46 of the housing body 30, which furtherdirects the gas G around the tube 40 in the flow direction d (see FIGS.4 and 5).

In certain embodiments, an exhaust flow path extends 360 degrees aboutthe circumference of the perforated tube 40, and the baffle plate 52coincides with only a portion the flow path. In certain embodiments anexhaust flow path extends 360 degrees about the circumference of theperforated tube 40, and the baffle plate 52 coincides with less thanone-third or less than one-quarter of the flow path. In certainembodiments, the main body 54 of the baffle plate 52 curves around onlya portion of the circumference of the perforated tube 40. In certainembodiments, an exhaust flow path extends 360 degrees about thecircumference of the perforated tube 40, the exhaust flow travels in asingle rotational direction about the perforated tube 40 along theexhaust flow path, the baffle plate 52 coincides with only a firstportion the exhaust flow path, and the louvers 62 encourage the flow inthe single rotational direction within the first portion of the exhaustflow path and assist in preventing exhaust from exiting the perforatedtube 40 along the first portion of the exhaust flow path. In certainembodiments, an exhaust flow path extends 360 degrees about thecircumference of the perforated tube 40, the exhaust flow travels in asingle rotational direction about the perforated tube 40 along theexhaust flow path, the baffle plate 52 coincides with only a firstportion the exhaust flow path, the louvers 62 of the baffle plate 52function as first swirl structures that encourage the flow in the singlerotational direction within the first portion of the exhaust flow path,and a curved portion 46 of an outer housing 30 that curves along aportion of the perforated tube 40 and coincides with a second portion ofthe exhaust flow path functions as a second swirl structure thatencourages the flow in the single rotational direction within the secondportion of the exhaust flow path.

As shown in FIGS. 4 and 5, a first portion 80 of the exhaust gas Gflowing through the housing 12 is directed though the open flow area A1and then in the first rotational direction d around the perforated tube40 (see FIGS. 4 and 5). The dosing and mixing unit 10 also is configuredsuch that also a second portion 82 of the exhaust gas flow passesthrough the flow-through openings 60 and is deflected in the firstrotation direction d about the perforated tube 40 by the louvers 62. Insome implementations, the second portion 82 proceeds at least 180° inthe first rotational direction d around the tube 40 before entering thetube 40 through the perforations. In certain implementations, the secondportion 82 proceeds at least 270° in the first rotational direction daround the tube 40 before entering the tube 40 through the perforations.In one example embodiment, second portion 82 proceeds at least 360° inthe first rotational direction d about the perforated tube 40 beforeentering the tube 40 through the perforations.

The main plate body 54 has a connected edge 64 that is connected to aninterior of the main housing body 30. In some implementations, the mainplate body 54 has a free edge 66 that extends across the interior volumeV of the main housing body 30. In such implementations, the main platebody 54 is sized and shaped to coincide with only a portion of thetransverse cross-sectional area A of the interior volume V such that anopen flow area A1 (see FIG. 9) is defined between the free edge 66 andthe interior of the main housing body 30. In some embodiments, the freeedge 66 is generally parallel to the tube axis 42 (see FIG. 9). In otherembodiments, the free edge 66 and the tube axis 42 can be angledrelative to one another.

In some implementations, a portion of the perforated tube 40 extendsbelow the free edge 66 of the baffle plate 52 and overlaps the open flowarea A1 (see FIG. 9). In some implementations, between about 10% of theperforated tube 40 and about 50% of the perforated tube 40 overlaps theopen flow area A1. In certain implementations, less than 40% of theperforated tube 40 overlaps the open flow area A1. In certainimplementations, less than 33% of the perforated tube 40 overlaps theopen flow area A1. In certain implementations, no less than 20% of theperforated tube 40 overlaps the open flow area A1. In certainimplementations, no less than 25% of the perforated tube 40 overlaps theopen flow area A1.

In other implementations, the main plate body 54 of the baffle 52extends fully across the interior volume V of the main housing body 30.In such implementations, the main plate body 54 defines an apertureseparate from the flow-through openings 60. The aperture extends over asignificant portion of the surface area of the main plate body 54 toexpose at least the portion of the cross-sectional area A locatedbeneath the tube 40. In certain implementations, the aperture also mayextend across a portion of the tube 40. For example, in someimplementations, the aperture extends over about 10% to about 60% of themain plate body 54. In certain implementations, the aperture extendsover about 20% to about 50% of the main plate body 54. In certainimplementations, the aperture extends over no less than 30% and no morethan 55% of the main plate body 54.

In still other implementations, first and second apertures can bedefined in the main plate body 54 separate from the flow-throughopenings 60. The first aperture aligns with a portion of the perforatedtube 40. The second aperture defines the open flow area (similar to openflow area A1 of FIG. 9). In certain implementations, the second aperturedoes not overlap with the perforated tube 40. In certainimplementations, the first aperture extends over no more than 20% of themain plate body 54 and the second aperture extends over no more than 30%of the main plate body 54.

In some implementations, the dosing and mixing unit 10 also can includea reactant dispenser 84 for dispensing reactant 86 within an interior ofthe perforated tube 40 such that the reactant 86 is mixed with theexhaust gas flow within the interior of the perforated tube 40 (see FIG.5). Examples of the reactant include, but are not limited to, ammonia,urea, or a hydrocarbon. In other embodiments, the reactant dispenser 84may be positioned upstream from the perforated tube 40 or downstreamfrom the perforated tube 40. The dispenser 84 can be aligned with thecenter axis 42 of the perforated tube 40 so as to generate a spraypattern concentric about the axis 42.

In some embodiments, a treatment substrate 99 is positioned downstreamfrom the perforated tube 40 (see FIG. 5). Example treatment substrates99 suitable for use with the tube 40 include, but are not limited to, alean NOx catalyst substrate, a SCR substrate, a SCRF substrate (i.e., aSCR coating on a particulate filter), and a NOx trap substrate. In someembodiments, the treatment substrate is an SCR substrate for treatingNOx and the reactant is selected from the group consisting of ammoniaand urea.

A selective catalytic reduction (SCR) catalyst device is typically usedin an exhaust system to remove undesirable gases such as nitrogen oxides(NOx) from the vehicle's emissions. SCR's are capable of converting NOxto nitrogen and oxygen in an oxygen rich environment with the assistanceof reactants such as urea or ammonia, which are injected into theexhaust stream upstream of the SCR through the doser 84. In alternativeembodiments, other aftertreatment devices such as lean NOx catalystdevices or lean NOx traps could be used in place of the SCR catalystdevice, and other reactants (e.g., hydrocarbons) can be dispensed by thedoser.

A lean NOx catalyst device is also capable of converting NOx to nitrogenand oxygen. In contrast to SCR's, lean NOx catalysts use hydrocarbons asreducing agents/reactants for conversion of NOx to nitrogen and oxygen.The hydrocarbon is injected into the exhaust stream upstream of the leanNOx catalyst. At the lean NOx catalyst, the NOx reacts with the injectedhydrocarbons with the assistance of a catalyst to reduce the NOx tonitrogen and oxygen. While the exhaust treatment systems 400 and 500will be described as including an SCR, it will be understood that thescope of the present disclosure is not limited to an SCR as there arevarious catalyst devices that can be used in accordance with theprinciples of the present disclosure.

The lean NOx traps use a material such as barium oxide to absorb NOxduring lean burn operating conditions. During fuel rich operations, theNOx is desorbed and converted to nitrogen and oxygen by reaction withhydrocarbons in the presence of catalysts (precious metals) within thetraps.

In other implementations, the dosing and mixing unit 10 can be used tomix hydrocarbons with the exhaust to reactivate a diesel particulatefilter (DPF). In such implementations, the reactant dispenser 84 injectshydrocarbons into the gas flow within the perforated tube 40. The mixedgas leaves the tube 40 and is directed to a downstream diesel oxidationcatalyst (DOC) at which the hydrocarbons ignite to heat the exhaust gas.The heated gas is then directed to the DPF to burn particulate cloggingthe filter.

As shown in FIGS. 10 and 11, some examples of the dosing and mixing unit10 also can include a perforated plate 105 positioned within the mainhousing body 30 of the dosing and mixing unit 10. In some embodiments,the perforated plate 105 is positioned between the inlet 18 and theexhaust treatment substrate 50. In some examples, the perforated plate105 includes a flat plate body 107 having a plurality of apertures 109to distribute the exhaust gas G within the main housing body 30 beforethe gas reaches the exhaust treatment substrate 50 (FIG. 12). In otherexamples, other types of flow distribution devices can be utilized. Instill other examples, no devices are positioned between the inlet 18 andthe exhaust treatment substrate 50.

In use of the dosing and mixing unit 10, exhaust enters the housing 12of the dosing and mixing unit 10 through the inlet 18 into the mainhousing body 30. From the inlet 18, the exhaust flow G moves through theperforated plate 105 (if utilized), through the substrate 50, and intothe interior volume V of the housing body 30 (see FIG. 4). At theinterior volume V, the first portion 80 of the exhaust gas G flows pastthe free edge 66 of the main body 54 of the baffle plate 52 and throughthe open area A1. Upon passing through the open area A1, the firstportion 80 of the exhaust flow G is directed toward the curved portion46 of the housing 12, which encourages the first portion 80 of theexhaust flow to flow in the first rotational direction d around a firstside 41 (see FIG. 3) of the perforated tube 40. In certainimplementations, some of the gas flow G can initially deflect off theupstream side 56 of the main body 54 of the baffle plate 52 towards thefree edge 66.

The second portion 82 of the exhaust gas flow G flows through theflow-through openings 60 of the baffle plate 52 from the upstream side56 of the main body 54 to the downstream side 58 of the main body 56.The second portion 82 of the exhaust gas flow G is deflected at thedownstream side 58 of the main body 54 with the louvers 62. Thisdeflection causes the second portion 82 of the exhaust gas flow G toflow in the first rotational direction d around a second side 43 (seeFIG. 3) of the perforated tube 40. The first and second sides 41, 43 areopposite sides of the perforated tube 40. As shown in FIG. 4, theexhaust gas (the combination of the first and second portions 80, 82)flows at least 270 degrees (preferably about 360 degrees) in the firstdirection d about the perforated tube 40.

The exhaust gas G swirling about the perforated tube 40 in the firstrotational direction d enters the openings in the perforated tube 40 andcontinues to swirl in the first rotational direction d within theperforated tube 40. The reactant dispenser 84 (see FIG. 5) dispensesreactant 86 into the swirling exhaust flow within the perforated tube40. The swirling of the exhaust gas causes the reactant 86 to be mixedwith the exhaust gas within the perforated tube 40. The exhaust flowthen exits the housing 12 through the outlet 18 defined by theperforated tube 40 and proceeds to the downstream exhaust treatmentsubstrate 99 (see FIG. 5). Mixing can continue as the exhaust gas flowsfrom the perorated tube 40 to the substrate 99.

Various modifications and alterations of this disclosure will becomeapparent to those skilled in the art without departing from the scopeand spirit of this disclosure, and it should be understood that thescope of this disclosure is not to be unduly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. A dosing and mixing arrangement comprising: amain body extending along a length between first and second oppositeends of the main body, the main body defining a longitudinal axisextending between the first and second ends, the main body also definingan interior accessible through an inlet; an outlet pipe extendingthrough the main body at a location adjacent the second end of the mainbody, the outlet pipe extending in a direction transverse to thelongitudinal axis of the main body; a mixing region disposed within theinterior of the main body, the mixing region including a perforatedconduit that extends transverse to the longitudinal axis of the mainbody, the perforated conduit defining multiple openings disposed along acircumference of the perforated conduit, the mixing region alsoincluding a flow path extending around the perforated conduit andleading into the perforated conduit through the multiple openings; and abaffle arrangement disposed within the interior of the main body, thebaffle arrangement defining a first entrance to the flow path, thebaffle arrangement also defining a second entrance to the flow path, thesecond entrance being spaced along the flow path from the firstentrance.
 2. The dosing and mixing arrangement of claim 1, wherein thebaffle arrangement includes a curved baffle plate having at least aportion extending between the perforated conduit and the inlet.
 3. Thedosing and mixing arrangement of claim 2, wherein the first entrance isdefined by a first aperture extending through the curved baffle plateand the second entrance is defined by a second aperture extendingthrough the curved baffle plate.
 4. The dosing and mixing arrangement ofclaim 1, wherein the outlet pipe is coupled to the perforated conduit.5. The dosing and mixing arrangement of claim 4, wherein the outlet pipeis a first section of a tube and the perforated conduit is a secondsection of the tube.
 6. The dosing and mixing arrangement of claim 4,wherein the outlet pipe has a constant diameter along a length of theoutlet pipe, the length of the outlet pipe extending transverse to thelongitudinal axis of the main body.
 7. The dosing and mixing arrangementof claim 1, wherein the perforated conduit has a constant diameter alonga length of the perforated conduit, the length of the perforated conduitextending transverse to the longitudinal axis of the main body.
 8. Thedosing and mixing arrangement of claim 1, wherein the baffle arrangementincludes a first curved surface positioned at the first entrance and asecond curved surface positioned at the second entrance.
 9. The dosingand mixing arrangement of claim 8, wherein both the first and secondcurved surfaces direct exhaust flow in a common direction along the flowpath.
 10. The dosing and mixing arrangement of claim 1, wherein thebaffle arrangement includes a curved baffle plate extending partiallyalong the perforated conduit, and wherein an open flow area is definedbetween the curved baffle plate and an opposing surface of the mainbody.
 11. The dosing and mixing arrangement of claim 10, wherein thefirst entrance leads to a portion of the flow path extending between thecurved baffle plate and the perforated conduit, and wherein the openflow region defines the second entrance.
 12. The dosing and mixingarrangement of claim 1, further comprising a substrate disposed withinthe interior of the main body and along a flow path between the inletand the perforated conduit.
 13. The dosing and mixing arrangement ofclaim 1, further comprising a reactant dispenser location disposed at anend of the perforated conduit.
 14. The dosing and mixing arrangement ofclaim 13, wherein the reactant dispensing location is aligned with acentral longitudinal axis of the perforated conduit, the centrallongitudinal axis extending through the outlet pipe.
 15. The dosing andmixing arrangement of claim 13, further comprising a reactant dispensermounted at the reactant dispenser location.
 16. The dosing and mixingarrangement of claim 1, wherein the inlet is disposed at the first endof the main body, wherein the longitudinal axis of the main body extendsthrough the inlet.
 17. The dosing and mixing arrangement of claim 1,wherein the multiple openings are disposed along a length of theperforated conduit.
 18. A dosing and mixing arrangement comprising: amain body extending along a length between first and second oppositeends of the main body, the main body defining a longitudinal axisextending between the first and second ends, the main body also definingan interior accessible through an inlet; an outlet pipe extendingthrough the main body at a location adjacent the second end of the mainbody, the outlet pipe extending in a direction transverse to thelongitudinal axis of the main body; a mixing region disposed within theinterior of the main body, the mixing region including a perforatedconduit that extends transverse to the longitudinal axis of the mainbody, the mixing region also including a flow path extending around theperforated conduit and leading into the perforated conduit; and a bafflearrangement disposed within the interior of the main body, the bafflearrangement defining a first entrance to the flow path, the bafflearrangement also defining a second entrance to the flow path, the secondentrance being spaced along the flow path from the first entrance, thebaffle arrangement including a curved baffle plate spaced from theperforated conduit so that the flow path passes through an open flowarea disposed between at least a portion of the baffle arrangement andan opposing surface of the perforated conduit.
 19. The dosing and mixingarrangement of claim 18, wherein the first entrance leads to a portionof the flow path extending between the curved baffle plate and theopposing surface of the perforated conduit, and wherein the open flowarea defines the second entrance.
 20. A dosing and mixing arrangementcomprising: a main body extending along a length between first andsecond opposite ends of the main body, the main body defining alongitudinal axis extending between the first and second ends, the mainbody also defining an interior accessible through an inlet; an outletpipe extending through the main body at a location adjacent the secondend of the main body, the outlet pipe extending in a directiontransverse to the longitudinal axis of the main body; a mixing regiondisposed within the interior of the main body, the mixing regionincluding a perforated conduit that extends transverse to thelongitudinal axis of the main body, the perforated conduit definingmultiple openings, the mixing region also including a flow pathextending around the perforated conduit and leading into the perforatedconduit through the multiple openings; and a baffle arrangement disposedwithin the interior of the main body, the baffle arrangement defining afirst entrance to the flow path, the baffle arrangement also defining asecond entrance to the flow path, the second entrance being spaced alongthe flow path from the first entrance, wherein the baffle arrangementincludes a curved baffle plate having at least a portion extendingbetween the perforated conduit and the inlet.
 21. A dosing and mixingarrangement comprising: a main body extending along a length betweenfirst and second opposite ends of the main body, the main body defininga longitudinal axis extending between the first and second ends, themain body also defining an interior accessible through an inlet; anoutlet pipe extending through the main body at a location adjacent thesecond end of the main body, the outlet pipe extending in a directiontransverse to the longitudinal axis of the main body; a mixing regiondisposed within the interior of the main body, the mixing regionincluding a perforated conduit that extends transverse to thelongitudinal axis of the main body, the perforated conduit definingmultiple openings, the mixing region also including a flow pathextending around the perforated conduit and leading into the perforatedconduit through the multiple openings; and a baffle arrangement disposedwithin the interior of the main body, the baffle arrangement defining afirst entrance to the flow path, the baffle arrangement also defining asecond entrance to the flow path, the second entrance being spaced alongthe flow path from the first entrance, wherein the baffle arrangementincludes a first curved surface positioned at the first entrance and asecond curved surface positioned at the second entrance.
 22. A dosingand mixing arrangement comprising: a main body extending along a lengthbetween first and second opposite ends of the main body, the main bodydefining a longitudinal axis extending between the first and secondends, the main body also defining an interior accessible through aninlet; an outlet pipe extending through the main body at a locationadjacent the second end of the main body, the outlet pipe extending in adirection transverse to the longitudinal axis of the main body; a mixingregion disposed within the interior of the main body, the mixing regionincluding a perforated conduit that extends transverse to thelongitudinal axis of the main body, the perforated conduit definingmultiple openings, the mixing region also including a flow pathextending around the perforated conduit and leading into the perforatedconduit through the multiple openings; and a baffle arrangement disposedwithin the interior of the main body, the baffle arrangement defining afirst entrance to the flow path, the baffle arrangement also defining asecond entrance to the flow path, the second entrance being spaced alongthe flow path from the first entrance, wherein the baffle arrangementincludes a curved baffle plate extending partially along the perforatedconduit, and wherein an open flow area is defined between the curvedbaffle plate and an opposing surface of the main body.